use Data::Dumper;
sub to_string {
  Data::Dumper->new([])->Terse(1)->Indent(0)->Useqq(1)->Values([$_[0]])->Dump;
}

say to_string(chr(13)); # "\r"
say to_string(chr(10)); # "\n"
say to_string(chr(97)); # "a"
say to_string(chr(31)); # "\37"